Alexander Hamilton was the first Secretary of the Treasury of the United States and a main contributor to The Federalist essays.  Hamilton made the decision to publish a series of essays defending the proposed Constitution and to explain in detail its principles. 

Alexander Hamilton recruited Madison and Jay to write the essays and chose Publius as the pseudonym under which the series would be written, in honor of Publius Valerius Publicola, one of the Roman aristocrats who overthrew the monarchy in 509 BC and who is credited with being instrumental in the founding of the Roman Republic.  Hamilton believed he would be instrumental with the founding of the American Republic. 

At the time of publication, the identity of the authors were kept secret up until Hamilton's death in 1804, when a list crediting him as one of the authors became public.  The list claimed that the majority of the essays were written by Hamilton, although some of these would later be disputed by Madison, who claimed to have written several of the articles credited to Hamilton.

Authored Federalist essays: nos. 1, 6-9, 11-13, 15-17, 18-20 (assisted Madison), 21-32, 34-36, 50-52 (with Madison), 54-58 (with Madison), 59-61, 62-63 (with Madison), 65-85

James Madison, the fourth president of the United States and "Father of the Constitution," was one of the principal founders of America's republican form of government. He was Hamilton's main collaborator on The Federalist essays, having written twenty-nine of the essays, although Madison and others since have claimed that he wrote more.

There is some evidence to support Madison's assertions--Hamilton's list incorrectly attributed No. 54 to John Jay, when in fact Jay wrote No. 64.  Because the authors themselves never released a complete list, no one will ever know for sure.

Authored Federalist essays: nos. 10, 14, 18-20 (assisted by Hamilton), 37-49, 50-52 (with Hamilton), 53, 54-58 (with Hamilton), 62-63 (with Hamilton)

John Jay was an American diplomat and politician. He was the author of five of The Federalist essays and later served as Chief Justice of the United States from 1789-1795.

Jay suffered an illness after contributing four essays, and he was only able to write one more before the end of the project, which explains the large gap between essays 5 and 64.

Authored Federalist essays: nos. 2-5, 64